Exchange It For a New Phone
One of the most obvious ways to get rid of a used phone is to exchange it. However, one will be surprised at how few users actually make use of this option. The biggest reason for not exchanging used phones is that the user will not get a satisfactory resale value for the phone. But like they say, something is better than nothing. And if you are looking at ways to get more out of your phone, then just check with your friends and relatives. They would definitely give you more than the mobile phone stores offer.
Give It Away
If you are not planning to buy a new phone, then another good idea is to just donate your phone to charity. There are several places where you can drop off your used phone and someone will find a good use for it and be extremely thankful for it too. You should contact your nearest old age home, or school for the differently-abled, or check with NGOs in your area.
If you have a phone which is capable of playing music, has FM and you can watch videos, it makes for a great PMP player (Personal Media Player). You can use this phone instead of spending money on a full featured MP3 player. The additional advantage is that you can use it for outdoor activities such as running or other sports where you would be hesitant to use your more expensive phone or a MP3 player.
If none of the above options suit you, then you should at least ensure that the phone is in absolutely perfect condition, with the batteries working fine and the respective chargers available. You can use this as a spare phone in case of loss or theft of your original phone. You can also carry the spare phone while you are travelling, instead of your more expensive phone. This will ensure that in case you lose or damage it, you will not regret it.